[Non-patent Document 1]
“Control Theory of Non-linear Mechanical Systems—A Passivity-based and Circuit-theoretic Approach”, by S. Arimoto, Oxford Science Publication, 1996.
[Non-patent Document 2]
“Bilateral Control with Energy Balance Monitoring Under Time-Varying communication Delay”, by Y. Yokokohji, T. Imaida, and T. Yoshikawa, Proceedings of the 2000 IEEE International Conference on Robotics and Automation, page 2684-2689, 2000.
[Non-patent Document 3]
“Control of a Flexible Manipulator with Noncollocated Feedback: Time Domain Passivity Approach”, by J. H. Ryu, D. S. Kwon, and B. Hannaford, Control Problems in Robotics, Springer Tracts in Advanced Robotics, Vol. 4, page 121-134, 2003.
To secure the safety of a control system, it is necessary to guarantee that “an object to be controlled is not brought to an unstable state (does not run away out of control) under any conditions”. On this account, it is common to add a hardware-like limiter (hardware limiter) to the control system.
On the other hand, passivity (for example, refer to non-patent document 1), which is the feature of a physical system, has received attention as a theoretical scheme to guarantee stability.
A system that monitors the energy balance of a specific system with attention given to passivity to limit accumulated energy to thereby secure stability is already proposed as energy balance monitor (non-patent document 2) and passivity observer/passivity controller (non-patent document 3). The conceptual diagram of these conventionally known systems is shown in FIG. 17.
By the way, evaluation criteria of the stability of a user's controlled object, which are used for determining the operation of a hardware limiter in a common control system, are the limitation of an operating range, the limitation of current and velocity for an actuator, and the like, which are rough in distinction between stability and instability. Moreover, there is also a possibility that once a limiter is activated in a system, the system is thereafter out of control and causes a secondary disaster. Even if the system does not come to cause a disaster, in many cases, it takes a great deal of time and labor to restart the system.
Further, the energy balance monitor of the non-patent document 2 secures the passivity of a transmission line between a master and a slave and the passivity observer/passivity controller of the non-patent document 3 secures the passivity of virtual space of a haptic system, respectively, but they do not guarantee the stability of a control system including an arbitrary control strategy, an arbitrary controlled object, and an arbitrary disturbance in a real world.
Still further, in the systems described in the non-patent documents 2, 3, on the assumption that the user's controlled object 3 is passive, the user's control strategy 5 is made virtually passive on the basis of the observation of energy balance to guarantee the stability of the whole system. However, if the user's controlled object 3 is not passive, the stability of the system cannot be guaranteed. Although most of the physical systems as the user's controlled object 3 are passive, the systems cannot cope with, for example, a situation where an actuator is connected in opposite polarity by mistake to operate opposite to a driving input. If not such an extreme example, the system cannot cope with also instability caused by disturbances having direct effect on the user's controlled object.
Therefore, it is an object of the present invention to provide a system configuration that can not be realized by a conventional technology, that is, keeps control performance as high as possible for a user's control system, which has its arbitrary user's controlled object controlled by an arbitrary user's control strategy and undergoes the effect of an arbitrary disturbance, and at the same time guarantees the stability of the user's controlled object.
Further, it is another object of the present invention to provide a system configuration that can evaluate the whole user's control system including all effects from the outside world and can guarantee the stability of the whole system.
Still further, it is still another object of the present invention to provide a system configuration that can guarantee the stability of a user's controlled object even if it is not assumed that the user's controlled object is passive.